The Major procedure of Soil nails construction
Setting out of soil nail position
The soil nail position should be located identical to that of the working plan, althoughsoil nail locations may be offset within the tolerances of specification agreed by designengineering. Before the drilling stage, cable detection and visual inspection shall be provided to avoid any buried utilities.
Drilling
The drilling rig is the equipment for drilling the soil nail drill hole. Before starting thedrilling process, the inclination and angle of drill mast should be checked to ensurethat they are the same as the design specified angle. Moreover, the drilling bit alsoneeds to meet the diameter requirement according the specification. Usually, most soilnail drilling uses a drill rig machine due to its easy delivery and simple maintenanceschedule. Some of them use a small hydraulic and mobile platform. But thisequipment is very expensive for operation, especially if the site is not accessible or thespace of working area is not available for drilling rig. Coring machines are alsosuitable for coring the soil nail hole. Traditional drilling rigs are powered bycompressed air which is provided by an air compressor machine.

Compressed air hastwo functions in the drilling rig. One is as a power source to drive the rotation of thedrill bit and push the drilling mast inward into the slope. The other function is whenthe drilling rig is operating; the compressed air can force the soil debris out of the hole.The drilled hole diameter usually should be in the range of 100mm to 150mm,depending on the size of the soil nail steel bar. In some case, an iron casing is providedwhen the soil property is loose dense and the drilled hole collapses easily.Un-grouted drill holes in soil should be kept open only for short periods of time.According to (CEDD GS vol2 section 7, 1992) standard, un-grouted drill holes shouldnot kept open for four days and for only 24 hours according to the Australian Standard.The longer the hole is left open, the greater the risk of collapse of drilled hole. If thehole is collapsed and unable for soil nail installation, a re-drill of the holes isnecessary.